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TALL BUILDINGDESIGN Steel, Concrete, and Composite Systems... Boca Raton London New York CRC Press is an imprint of theTaylor & Francis Group, an informa business TALL BUILDING DESIGN Bu

TALL BUILDING

DESIGN

Steel, Concrete, and Composite Systems

Boca Raton London New York CRC Press is an imprint of the

Taylor & Francis Group, an informa business

TALL BUILDING

DESIGN Bungale S Taranath, Ph.D., P.E., S.E.

Steel, Concrete, and Composite Systems

Taylor & Francis Group

6000 Broken Sound Parkway NW, Suite 300

Boca Raton, FL 33487-2742

© 2017 by Taylor & Francis Group, LLC

CRC Press is an imprint of Taylor & Francis Group, an Informa business

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Version Date: 20160610

International Standard Book Number-13: 978-1-4665-5620-1 (Hardback)

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Library of Congress Cataloging‑in‑Publication Data

1 Building, Iron and steel 2 Concrete construction 3 Composite construction 4 Tall

buildings Design and construction I Title

My dearest and best friend, whose considerable expertise and interest in all aspects of life has influenced my entire existence including my book-writing avocation.

Contents

Preface xxiii

Acknowledgments xxix

Special.Acknowledgment xxxi

Author xxxiii

Chapter 1 Loads.on.Building.Structures 1

Preview 1

Dead.Loads 2

Occupancy.Loads.on.Buildings 2

Snow.Loads.on.Buildings 2

1.1 Dead.Loads 3

1.2 Live.Loads 7

1.2.1 Live.Load.Reduction 10

1.3 Construction.Loads 11

1.4 Lateral.Soil.Load 14

1.5 Snow,.Rain,.and.Ice.Loads 15

1.6 Thermal.and.Settlement.Loads 16

1.7 Self-Straining.Forces 18

1.8 Dynamic.Loads 18

1.9 Abnormal.Loads 19

1.9.1 Explosion.Effects 19

1.9.2 Floods 20

1.9.3 Vehicle.Impact.Loads 20

1.10 .Classification.of.Buildings,.Risk.Categories,.and.Importance.Factors 20

Chapter 2 Wind.Loads 23

Preview 23

2.1 Description.of.Wind.Forces 23

2.2 Types.of.Wind.Storms 31

2.2.1 Straight-Line.Wind 31

2.2.2 Down-Slope.Wind 31

2.2.3 Downburst 31

2.2.4 Northeastern.Winds 33

2.2.5 Thunderstorm 33

2.2.6 Hurricane 33

2.2.7 Tornado 34

2.2.8 Statistical.Likelihood.of.Natural.Hazards 36

2.2.9 Probabilistic.Approach.in.Wind.Engineering 39

2.3 Wind/Building.Interactions 40

2.3.1 Exposure.Categories 40

2.3.2 Basic.Wind.Speed 40

2.3.3 Topography 41

2.3.4 Building.Height 41

2.3.5 Internal.Pressure 42

2.3.6 Aerodynamic.Pressure 42

2.3.7 Probability.of.Occurrence 43

2.3.7.1 Routine.Winds 44

2.3.7.2 Stronger.Winds 44

2.3.7.3 Design.Level.Winds 44

2.3.7.4 Tornadoes 45

2.4 Behavior.of.Tall.Buildings.Subjected.to.Wind 45

2.4.1 Properties.of.the.Mean.Wind.Loads 47

2.4.1.1 Variation.of.Wind.Velocity.with.Height 48

2.4.1.2 Wind.Turbulence 49

2.4.2 Action.of.Wind.on.Tall.Buildings 50

2.4.3 Dynamic.Action.of.Wind 51

2.4.4 Buffeting.due.to.Vortex.Shedding 51

2.4.5 Aerodynamic.Damping 55

2.4.6 Design.Criteria.for.Wind 56

2.4.7 Building.Sway 57

2.5 Scope,.Effectiveness,.and.Limitations.of.Building.Codes 58

2.5.1 Scope 58

2.5.2 Effectiveness 59

2.5.3 Limitations 59

2.6 ASCE.7-10.Wind.Load.Provisions,.Overview 59

2.6.1 Design.Wind.Loads.for.Main.Wind-Force-Resisting.Systems 59

2.6.2 Design.Wind.Pressures.for.Components.and.Cladding 62

2.6.2.1 Distribution.of.Pressures.and.Suctions 64

2.6.2.2 Local.Cladding.Loads.and.Overall.Design.Loads 66

2.6.3 Comments.on.ASCE.7-10.Wind.Provisions 68

Chapter 3 Earthquake.Effects.on.Buildings 69

Preview 69

3.1 Inertial.Forces.and.Acceleration 72

3.2 Duration,.Velocity,.and.Displacement 74

3.3 Acceleration.Amplification.due.to.Soft.Soil 74

3.4 Natural.Periods 75

3.5 Building.Resonance 76

3.6 Site.Response.Spectrum 77

3.7 Damping 79

3.8 Ductility 80

3.9 Earthquakes.and.Other.Geologic.Hazards 80

3.10 Earthquake.Measurements 81

3.11 Determination.of.Local.Earthquake.Hazards 82

3.11.1 Probabilistic.Seismic.Hazard.Analysis 84

3.11.2 Range.of.Earthquake.Performance.Criteria 86

3.12 Nonstructural.Components 86

3.12.1 Response.of.Elements.Attached.to.Buildings 88

3.13 Seismic.Analysis.Procedures 88

3.13.1 Equivalent.Lateral.Force.Procedure 88

3.13.2 Linear.Dynamic.Analysis 89

3.14 System.Selection 89

3.14.1 Elastic.Behavior 89

3.14.2 Postelastic.Behavior 89

3.14.3 Cyclic.Behavior 90

3.15 Seismic.Issues.due.to.Configuration.Irregularities 91

3.15.1 Vertical.Lateral-Load-Resisting.Systems 92

3.15.1.1 Shear.Walls 92

3.15.1.2 Braced.Frames 93

3.15.1.3 Moment-Resistant.Frames 93

3.15.2 Diaphragms 95

3.15.2.1 Collectors 96

3.15.2.2 Role.of.Diaphragms 97

3.15.2.3 Types.of.Diaphragms 97

3.15.2.4 Diaphragm.Design.Procedures 99

3.15.2.5 Shear.Transfer.from.Diaphragm.to.VLLRS 99

3.15.2.6 Modeling.of.Rigid.Diaphragms 103

3.15.3 Optimizing.Structural.Configuration 105

3.15.4 Effects.of.Configuration.Irregularity 109

3.15.4.1 Stress.Concentrations 109

3.15.4.2 Torsion 109

3.15.5 Configuration.Irregularities.in.Seismic.Standards 110

3.15.6 Four.Serious.Configuration.Conditions 111

3.15.6.1 Soft.and.Weak.Stories 112

3.15.6.2 Discontinuous.Shear.Walls 113

3.15.6.3 Variations.in.Perimeter.Strength.and.Stiffness 114

3.15.6.4 Reentrant.Corners 116

3.15.7 Other.Seismic.Issues 118

3.15.7.1 P-Delta.Effect 118

3.15.7.2 Strong.Beam,.Weak.Column 120

3.15.7.3 Setbacks.and.Planes.of.Weakness 120

3.15.8 Earthquake.Collapse.Patterns 120

3.15.8.1 Unintended.Addition.of.Stiffness 121

3.15.8.2 Inadequate.Beam–Column.Joint.Strength 122

3.15.8.3 Tension/Compression.Failures 122

3.15.8.4 Wall-to-Roof.Connection.Failure 123

3.15.8.5 Local.Column.Failure 123

3.15.8.6 Heavy.Floor.Collapse 123

3.15.8.7 Torsion.Effects 124

3.15.8.8 Soft-Story.Collapse 124

3.15.8.9 Midstory.Collapse 124

3.15.8.10 Pounding 124

3.15.9 Conclusions 125

3.16 Structural.Dynamic 126

3.16.1 Dynamic.Loads 127

3.16.2 Concept.of.Dynamic.Load.Factor 128

3.16.3 Difference.between.Static.and.Dynamic.Analyses 130

3.16.4 Dynamic.Effects.due.to.Wind.Gusts 133

3.16.5 Characteristics.of.a.Dynamic.Problem 134

3.16.6 Multiple.Strategy.of.Seismic.Design 136

3.16.7 Example.of.Portal.Frame.Subject.to.Ground.Motions 137

3.16.8 Concept.of.Dynamic.Equilibrium 138

3.16.9 Free.Vibrations 140

3.16.10 Earthquake.Excitation 141

3.16.11 Single-Degree-of-Freedom.Systems 141

3.16.12 Numerical.Integration.Technique 142

3.16.13 Summary.of.Numerical.Integration.Technique 145

3.16.14 Summary.of.Structural.Dynamics 146

3.17 Response.Spectrum.Method 148

3.17.1 Earthquake.Response.Spectrum 152

3.17.2 Deformation.Response.Spectrum 154

3.17.3 Pseudovelocity.Response.Spectrum 154

3.17.4 Pseudoacceleration.Response.Spectrum 156

3.17.5 Tripartite.Response.Spectrum:.Combined Displacement–Velocity–Acceleration.Spectrum 156

3.17.6 Characteristics.of.Response.Spectrum 159

3.17.7 Difference.between.Design.and.Actual.Response.Spectra 162

3.17.8 Summary.of.Response.Spectrum.Analysis 162

3.17.9 Hysteresis.Loop 164

3.17.10 Seismology 167

3.18 Seismic.Design.Considerations 168

3.18.1 Seismic.Response.of.Buildings 170

3.18.2 Building.Motions.and.Deflections 172

3.18.3 Building.Drift.and.Separation 172

3.18.4 Adjacent.Buildings 173

3.18.5 Continuous.Load.Path 173

3.18.6 Building.Configuration 174

3.18.7 Influence.of.Soil 176

3.18.8 Ductility 178

3.18.9 Redundancy 178

3.18.10 Damping 179

3.18.11 Diaphragms 182

3.18.12 Strategies.to.Reduce.Seismic.Hazards 184

3.18.13 Strategies.to.Improve.Building.Seismic.Performance 185

3.19 Lessons.from.Past.Earthquakes 185

3.19.1 1906.San.Francisco.Earthquake 185

3.19.2 1933.Long.Beach.Earthquake 186

3.19.3 1940.Imperial.Valley.and.1952.Kern.County.Earthquakes 186

3.19.4 1971.San.Fernando.Earthquake 186

3.19.5 1979.Imperial.Valley.Earthquake 187

3.19.6 1985.Mexico.City.Earthquake 187

3.19.7 1987.Whittier.Narrows.Earthquake 187

3.19.8 1989.Loma.Prieta.Earthquake 188

3.19.9 1994.Northridge.Earthquake 188

3.20 Seismic.Design.Wrap-Up 189

3.20.1 Determination.of.Earthquake.Lateral.Forces 190

3.20.2 Structural.Response 191

3.20.3 Equivalent.Lateral.Load.Procedure 192

3.20.4 Architectural.Implications 193

3.20.5 Structural.Concept 194

3.20.6 Damage.Control.Features 195

3.20.7 Techniques.of.Seismic.Design 195

3.21 Dynamic.Analysis,.Theory 197

3.21.1 Single-Degree-of-Freedom.Systems 197

3.21.2 Multidegree-of-Freedom.Systems 200

3.21.3 Modal.Superposition 202

3.21.4 Normal.Coordinates 202

3.21.5 Orthogonality 204

3.21.6 Design.Example:.Dynamic.Displacement 210

3.22 Anatomy.of.Computer.Response.Spectrum.Analyses 210

3.22.1 Example.1:.Three-Story.Building 211

3.22.2 Example.2:.Seven-Story.Building 212

Chapter 4 Wind.Load.Analysis.of.Buildings 223

Preview 223

4.1 Major.Causes.of.Wind.Forces 223

4.2 Building.Codes.Addressing.Wind.Loads.and.Floods 226

4.3 Basic.Wind.Engineering.Concepts 227

4.4 Organization.of.ASCE.7-10.for.Wind.Load.Calculations 228

4.5 General.Requirements.of.Wind.Load.Calculations 228

4.5.1 MWRFS.and.C.&.C 228

4.5.2 General.Requirements 228

4.5.3 Wind.Directionality.Factor.(K d) 230

4.5.4 Exposure.Category 230

4.5.5 Topographic.Factor.(K zt) 232

4.5.6 Gust.Effects 232

4.5.7 Enclosure.Classifications 233

4.5.8 Internal.Pressure.Coefficient.(GCpi) 234

4.5.9 Structural.Damping 234

4.6 Wind.Velocity.Pressure 234

4.7 Directional.Procedure.(Chapter.27,.ASCE.7-10) 235

4.8 Envelope.Procedure.(Chapter.28,.ASCE.7-10) 239

4.9 .Other.Structures.and.Building.Appurtenances.(Chapter.29,.ASCE.7-10) 240

4.10 Components.and.Cladding.(Chapter.30,.ASCE.7-10) 242

4.11 Significant.Changes.in.ASCE.7-10.as.Compared.to.ASCE.7-05 246

4.12 Solved.Examples 249

4.13 Wind.Tunnel.Procedure 256

4.13.1 Test.Requirements 256

4.13.2 Load.Effects.and.Limitations 257

4.13.3 Types.of.Wind.Tunnel.Tests 257

4.13.3.1 Rigid.Pressure.Model 258

4.13.3.2 High-Frequency.Base.Force.Balance.Model.(H-FBBM) 260

4.13.3.3 Aero-Elastic.Model 264

4.13.4 Lower.Limits.on.Wind.Tunnel.Test.Results 267

4.13.5 Structural.Properties.Required.for.Wind.Tunnel.Data.Analysis 268

4.13.5.1 Natural.Frequencies.and.Mode.Shapes 268

4.13.5.2 Mass.Distribution 269

4.13.5.3 Damping.Ratio 269

4.13.6 Building.Drift 269

4.14 Human.Response.to.Wind-Induced.Building.Motions 270

4.15 Building.Periods 272

4.16 Pedestrian.Wind.Studies 273

Chapter 5 Seismic.Design.with.Particular.Reference.to.ASCE.7-10.Seismic.Provisions 277

Preview 277

5.1 ASCE.7-10,.Chapter.11,.Seismic.Design.Criteria 278

5.1.1 Alternate.Materials.and.Alternate.Means.and.Methods of Construction 279

5.1.2 Seismic.Ground.Motion.Values,.S s and.S1 279

5.1.2.1 Mapped.Acceleration.Parameters 281

5.1.3 Site.Coefficients.and.Adjusted.Acceleration.Parameters 282

5.1.3.1 Site.Class.S A , S B , S C , S D , S E ,.and.S F 282

5.1.4 Design.Response.Spectrum 283

5.1.4.1 Design.Base.Shear 284

5.1.5 Site-Specific.Ground.Motion.Procedures 286

5.1.6 Importance.Factor.and.Occupancy.Category 288

5.1.6.1 Importance.Factor.I E 289

5.1.6.2 Protected.Access.for.Category.IV.Structures 290

5.1.7 Seismic.Design.Categories 290

5.1.8 Design.Requirements.for.Seismic.Design.Category.A 292

5.1.8.1 Lateral.Forces 293

5.1.8.2 Anchorage.of.Concrete.or.Masonry.Walls 294

5.1.9 Site.Limitations.for.Seismic.Design.Categories.E.and.F 295

5.1.10 Additional.Geotechnical.Investigation.Report.Requirements for Seismic.Design.Categories.D,.E,.and.F 295

5.2 ASCE.7-10,.Chapter.12,.Seismic.Design.Requirements.for.Building Structures 295

5.2.1 Basic.Requirements 296

5.2.2 Member.Design,.Connection.Design,.and.Deformation.Limit 299

5.2.3 Continuous.Load.Path.and.Interconnection 299

5.2.3.1 R,.C d,.and.Ωo.Values.for.Vertical.Combinations 301

5.2.3.2 R,.C d,.and.Ωo.Values.for.Horizontal.Combinations 302

5.2.4 Dual.System 302

5.2.5 Irregular.and.Regular.Classification 302

5.2.5.1 Plan.(Horizontal).Irregularity 302

5.2.5.2 Vertical.Irregularity 303

5.2.5.3 Prohibited.Horizontal.and.Vertical.Irregularities in Seismic.Design.Categories.D.through.F 304

5.2.5.4 Elements.Supporting.Discontinuous.Walls.or.Frames 304

5.2.6 Increase.in.Forces.due.to.Irregularities.for.Seismic.Design Categories.D.through.F 305

5.2.7 Redundancy 305

5.2.7.1 Redundancy.Factor,.p,.for.Seismic.Design.Category.D. through.F 305

5.2.8 Seismic.Load.Effect.and.Combinations 308

5.2.9 Direction.of.Loading 309

5.2.10 Analysis.Procedure 309

5.2.11 Foundation.Modeling.Criteria 310

5.2.12 Effective.Seismic.Weight 310

5.2.13 Structural.Modeling 310

5.2.14 Interaction.Effects 311

5.2.15 Equivalent.Lateral.Force.Procedure 311

5.2.16 Seismic.Base.Shear 312

5.2.17 Period.Determination 313

5.2.17.1 Vertical.Distribution.of.Seismic.Force 314

5.2.17.2 Seismic.Loads.due.to.Vertical.Ground.Motions 316

5.2.18 Horizontal.Distribution.of.Forces 316

5.2.19 Inherent.and.Accidental.Torsion 317

5.2.20 Story.Drift.Determination 318

5.2.21 Period.for.Computing.Drift 319

5.2.22 P-Delta.Effects 319

5.2.23 Analysis.Procedures.with.Particular.Emphasis.on.Response Spectrum.Analysis 320

5.2.23.1 Number.of.Modes 323

5.2.23.2 Modal.Response.Parameters 323

5.2.23.3 Scaling.Design.Values.of.Combined.Response 324

5.2.23.4 Horizontal.Shear.Distribution 324

5.2.23.5 Deflection.Amplification.due.to.P-Delta.Effects 324

5.2.23.6 Seismic-Force.Distribution.for.Diaphragm.Design 327

5.2.24 Drift.and.Deformation 330

5.2.25 Building.Separation 333

5.2.26 Deformation.Compatibility.for.Seismic.Design.Categories D,.E,.and.F 334

5.2.27 Catalog.of.Seismic.Design.Requirements.for.Buildings Assigned.to.SDC.A,.B,.C,.D,.E,.or.F 335

5.2.27.1 Buildings.in.SDC.A 336

5.2.27.2 SDC.B.Buildings 337

5.2.27.3 SDC.C.Buildings 338

5.2.27.4 SDC.D.Buildings 339

5.2.27.5 SDC.E.Buildings 341

5.2.27.6 SDC.F.Buildings 341

Chapter 6 Performance-Based.Design 343

Preview 343

6.1 Definitions.of.Performance-Based.Design 344

6.2 Prescriptive.Approach.to.Codes 344

6.3 Performance-Based.Approach 344

6.3.1 Performance-Based.Design.for.Natural.Hazards 345

6.3.2 Performance-Based.Seismic.Design 346

6.3.2.1 Determining.Acceptable.Risk 346

6.3.3 Expected.Performance.When.Designing.to.Current.Codes 348

6.3.4 Expected.Performance.of.Structural.Components 348

6.3.5 Expected.Performance.of.Nonstructural.Components 348

6.4 Improving.Performance.to.Reduce.Seismic.Risk 349

6.4.1 Selection.of.Structural.Materials.and.Systems 349

6.4.2 Selection.of.the.Architectural.Configuration 350

6.4.3 Consideration.of.Nonstructural.Component.Performance 350

6.5 .Design.and.Performance.Issues.Relating.to.Commercial.Office.Buildings 351

6.5.1 Performance.of.Office.Buildings.in.Past.Earthquakes 351

6.5.2 Performance.Expectations.and.Requirements 352

6.5.3 Seismic.Hazard.and.Site.Issues 352

6.5.4 Structural.System.Issues 352

6.5.5 Nonstructural.System.Issues 353

6.6 Current.Specifications.for.Performance-Based.Seismic.Design 353

6.6.1 Building.Performance.Objectives 354

6.6.2 Building.Performance.Levels 354

6.6.2.1 Operational.Level 354

6.6.2.2 Immediate.Occupancy.Level 354

6.6.2.3 Life-Safety.Level 354

6.6.2.4 Collapse.Prevention.Level.or.Near-Collapse.Level 355

6.6.2.5 Alternative.Design.Criteria:.2008.LATBSDC 355

6.6.3 Recommended.Administrative.Bulletin.on.the.Seismic.Design and.Review.of.Tall.Buildings.Using.Nonprescriptive.Procedures AB-083 356

6.7 Closing.Comments 356

Chapter 7 Preliminary.Calculations.to.Ensure.Validity.of Computer.Analysis 359

Preview 359

7.1 Characterizing.Structural.Behavior 360

7.1.1 History.of.Structural.Engineering 363

7.1.2 Design.Process 365

7.1.2.1 Conceptual.Stage 365

7.1.2.2 Preliminary.Design.Stage 365

7.1.2.3 Selection.Stage 365

7.1.2.4 Final.Design.Stage 366

7.1.2.5 Construction.Stage 366

7.1.3 Basic.Principles.of.Structural.Analysis 366

7.1.3.1 Requirements.of.Structural.Analysis 367

7.1.3.2 Equilibrium.Requirements 367

7.2 Advantages.and.Disadvantages.of.Indeterminate.Structures 368

7.2.1 Free-Body.Diagrams 369

7.2.2 Stiffness.Requirements 370

7.2.3 Kinematic.Requirements 370

7.2.4 Analysis.Summary 370

7.2.5 Braced.Frames.as.Beams 371

7.2.6 Preliminary.Analysis.of.Rigid.Frames 373

7.2.6.1 Portal.Method 376

7.2.6.2 Drift.Assessment—Frame.Structures 382

7.2.6.3 Deflection.Calculations 386

7.2.6.4 Design.Examples,.Portal.and.Cantilever.Methods 391

7.2.6.5 Framed.Tubes 393

7.3 Preliminary.Design:.Concrete 395

7.3.1 Preliminary.Design:.Concrete.Columns 395

7.3.2 Preliminary.Design.of.PT.Floor.Systems 396

7.3.2.1 Simple.Span.Beam 399

7.3.2.2 Continuous.Beams 402

7.3.3 Concept.of.Secondary.Moments 422

7.3.3.1 Secondary.Moment 424

7.3.4 Strength.Design.for.Flexure 432

7.3.5 Guidelines.for.Thinking.on.Your.Feet 440

7.3.6 Unit.Quantities:.Reinforced.Concrete.Buildings 440

7.3.7 Unit.Quantity.of.Reinforcement.in.Columns 446

7.3.8 Unit.Quantity.of.Reinforcement.and.Concrete.in Floor-Framing Systems 451

7.4 Estimation.of.Preliminary.Wind.Loads,.ASCE.7-10 451

7.5 Preliminary.Seismic.Base.Shear,.V,.as.a.Percent.of.Building’s Seismic Weight,.W 457

7.5.1 Building.Height,.hn.=.160.ft 463

7.5.2 Buildings.Taller.than.160.ft 463

7.6 Differential.Shortening.of.Steel.Columns 477

7.6.1 Simplified.Method.of.Calculating.Δz,.Axial.Shortening of Columns 478

7.6.2 Derivation.of.Simplified.Expression.for.A z 478

7.6.3 Column.Length.Corrections,.Δc 486

7.6.4 Column.Shortening.Verification.during.Construction 486

7.7 Guidance.for.Preparing.Conceptual.Estimates 487

7.8 Concept.of.Premium.for.Height 491

Chapter 8 Seismic.Evaluation.and.Rehabilitation.of Existing.Buildings 493

Preview 493

8.1 Code-Sponsored.Design 495

8.1.1 Building.Deformations 497

8.2 Alternate.Design.Philosophy 498

8.2.1 Initial.Considerations 501

8.2.2 Rehabilitation.Objective 502

8.2.2.1 Performance.Levels 502

8.2.2.2 Seismic.Hazard 502

8.2.2.3 Selecting.a.Rehabilitation.Objective 502

8.2.2.4 Rehabilitation.Method 503

8.2.2.5 Rehabilitation.Strategy 503

8.2.3 Analysis.Procedures 503

8.2.4 Verification.of.Rehabilitation.Design 504

8.2.5 Nonstructural.Risk.Mitigation 504

8.2.5.1 Disabled.Access.Improvements 504

8.2.5.2 Hazardous.Material.Removal 504

8.2.5.3 Design,.Testing.and.Inspection, and Management Fees 504

8.2.5.4 Historic.Preservation.Costs 505

8.3 .Seismic.Rehabilitation.of.Existing.Buildings:.ASCE/SEI.Standard.41-06 505

8.3.1 Overview.of.Performance.Levels 507

8.3.2 Permitted.Design.Methods 509

8.3.3 Systematic.Rehabilitation 509

8.3.3.1 Determination.of.Seismic.Ground.Motions 510

8.3.3.2 Determination.of.As-Built.Conditions 510

8.3.3.3 Primary.and.Secondary.Components 511

8.3.3.4 Setting.Up.Analytical.Model.and.Determination of Design.Forces 511

8.3.3.5 Combined.Gravity.and.Seismic.Demand 513

8.3.3.6 Component.Capacity.Calculations.Q CE and.Q CL 514

8.3.4 Development.of.Concepts.for.Seismic.Upgrading 515

8.3.4.1 Structural.Systems 516

8.3.4.2 Configuration 517

8.3.4.3 Horizontal.Diaphragms.and.Foundation.Ties 517

8.3.4.4 Eccentricity 517

8.3.4.5 Deformation.Compatibility.of.New.and.Existing Materials 517

8.3.4.6 Base.Isolation.and.Energy.Dissipation 518

8.3.4.7 Selection.of.Strengthening.Technique 519

8.3.5 Seismic.Risk.Reduction.Strategies 519

8.3.5.1 Reduce.Site.Hazards 520

8.3.5.2 Improve.Building.Performance 520

8.3.6 ASCE/SEI.41-06:.Seismic.Evaluation.Example:.Steel.Building 521

8.3.7 ASCE/SEI.41-06:.Seismic.Evaluation:.Concrete.Building 526

8.4 .Common.Deficiencies.and.Upgrade.Methods:.Concrete.Building 530

8.4.1 Diaphragms 531

8.4.1.1 Cast-in-Place.Concrete.Diaphragms 531

8.4.1.2 Precast.Concrete.Diaphragms 534

8.4.2 Shear.Walls 534

8.4.2.1 Increasing.Wall.Thickness 534

8.4.2.2 Increasing.Shear.Strength.of.Wall 535

8.4.2.3 Infilling.between.Columns 535

8.4.2.4 Addition.of.Boundary.Elements 536

8.4.2.5 Addition.of.Confinement.Jackets 536

8.4.2.6 Repair.of.Cracked.Coupling.Beams 536

8.4.2.7 Adding.New.Walls 536

8.4.2.8 Precast.Concrete.Shear.Walls 536

8.4.3 Infilling.of.Moment.Frames 537

8.4.4 Reinforced.Concrete.Moment.Frames 537

8.4.5 Open.Storefront 538

8.4.6 Clerestory 538

8.4.7 Shallow.Foundations 538

8.4.8 Rehabilitation.Measures.for.Deep.Foundations 540

8.4.9 Nonstructural.Elements 540

8.4.9.1 Life.Safety 541

8.4.9.2 Property.Loss 541

8.4.9.3 Loss.of.Function 541

8.4.9.4 Causes.of.Nonstructural.Damage 542

8.4.9.5 Design.Procedure.for.Nonstructural.Components 543

8.4.9.6 Seismic.Hazard 544

8.4.9.7 Non-Load-Bearing.Walls 544

8.4.9.8 Precast.Concrete.Cladding 545

8.4.9.9 Stone.or.Masonry.Veneers 545

8.4.9.10 Building.Ornamentation 545

8.4.9.11 Acoustical.Ceiling 546

8.4.10 Fiber-Reinforced.Polymer.Systems.for.Strengthening of Concrete.Buildings 546

8.4.10.1 Mechanical.Properties.and.Behavior 546

8.4.10.2 Design.Philosophy 547

8.4.10.3 Flexural.Design 547

8.5 Concluding.Remarks 547

8.6 Seismic.Strengthening.Details 551

Chapter 9 Special.Topics 621

9.1 Serviceability.Considerations 621

9.1.1 Deflections 622

9.1.2 Building.Drift 623

9.1.3 Vibrations 623

9.1.4 Design.for.Long-Term.Deflection 625

9.1.5 Camber 625

9.1.5.1 Recommended.Camber.Criteria 626

9.1.6 Expansion.and.Contraction 625

9.1.7 Durability 625

9.1.8 Serviceability.Considerations:.Concrete.Systems 625

9.1.9 Tall.Building.Motions 627

9.1.10 Building.Motion.Perception 629

9.1.11 Structural.Damping 629

9.2 Damping.Devices.for.Reducing.Motion.Perception 631

9.2.1 Passive.Viscoelastic.Dampers 631

9.2.2 Tuned.Mass.Damper 633

9.2.2.1 Tuned.Mass.Damper:.Simple.Pendulum.Type 634

9.2.2.2 Tuned.Mass.Damper:.Linked.Pendulum.Type 634

9.2.2.3 Citicorp.Tower,.New.York 634

9.2.2.4 John.Hancock.Tower,.Boston,.MA 636

9.2.2.5 Design.Considerations.for.Tuned.Mass.Damper 637

9.2.3 Tuned.Sloshing.Damper 637

9.2.4 Tuned.Liquid.Column.Damper 637

9.2.4.1 Wall.Center,.Vancouver,.BC 639

9.2.4.2 Highcliff.Apartment.Building,.Hong.Kong 639

9.2.5 Simple.Pendulum.Damper 641

9.2.5.1 Taipei.Financial.Center 641

9.2.5.2 Nested.Pendulum.Damper 642

9.3 Seismic.Isolation 642

9.3.1 Salient.Features 645

9.3.2 Mechanical.Properties.of.Seismic.Isolation.Systems 645

9.3.3 Elastomeric.Isolators 647

9.3.4 Sliding.Isolators 647

9.3.5 Seismically.Isolated.Structures:.ASCE.7-10.Design.Provisions 648

9.3.5.1 Illustrative.Example:.Static.Procedure 651

9.3.5.2 Building.Characteristics 652

9.3.5.3 Triple.Pendulum.Bearing 662

9.3.5.4 Additional.Notes.on.Friction.Pendulum.Systems 663

9.4 Passive.Energy.Dissipation 664

9.5 Blast-Resistant.Design 666

9.5.1 Design.Criteria 668

9.5.2 Load.Criteria 668

9.5.3 Analysis.Procedure 668

9.5.4 Difference.between.Seismic.and.Blast-Resistant.Design 669

9.5.5 Selection.of.Design.Blast.Load 670

9.5.6 Design.Summary 672

9.5.7 Progressive.Collapse 673

9.5.7.1 Design.Alternatives.for.Reducing.Progressive.Collapse 673

9.5.7.2 Guidelines.for.Achieving.Structural.Integrity 673

9.6 Failures.and.Distresses 674

9.6.1 Kemper.Arena.Roof.Collapse 675

9.6.2 Hartford.Arena.Roof.Collapse 677

9.6.3 Ronan.Point:.Progressive.Collapse 679

9.6.4 Standard.Oil.of.Indiana.Building,.Chicago:.Curtain.Wall.Distress 681

9.6.5 Hancock.Tower,.Boston:.Curtain.Wall.Distress 682

9.6.6 Hyatt.Regency.Walkways.Collapse 683

9.7 Buckling.of.Building.under.Its.Own.Weight 689

9.7.1 Circular.Building 690

9.8 Foundations 691

9.8.1 Footings,.Mats,.and.Piles 691

9.8.2 Grade.Beams.and.Slab.on.Grade 691

9.8.3 Piles,.Piers,.and.Caissons 692

9.8.4 Effect.of.Seismic.Forces.on.Foundation.Design 692

9.8.4.1 Footing.and.Raft.Foundations 692

9.8.4.2 Pile.Foundation 692

9.8.4.3 Load.Capacity.of.Piles 693

9.9 Evolution.of.High-Rise.Architecture 693

9.9.1 Architectural.Review 695

9.9.2 Prototype.of.Today.(2013) 696

9.9.3 Structural.Systems.for.Selected.Tall.Buildings 700

9.9.3.1 Taipei.101 700

9.9.3.2 Jin.Mao.Tower,.Shanghai,.China 703

9.9.3.3 Petronas.Towers,.Kuala.Lumpur,.Malaysia 705

9.9.3.4 World.Trade.Center.Towers,.New.York 706

9.9.3.5 Empire.State.Building,.New.York 710

9.9.3.6 Bank.of.China.Tower,.Hong.Kong 711

9.9.3.7 Standard.Oil.of.Indiana.Building,.Chicago 712

9.10 Post-Tension.Strengthening.of.Existing.Structures 715

9.10.1 Tendon.Profiles 715

9.10.2 Supports 715

9.10.3 Anchorages 715

9.10.4 Tendon.Protection 716

9.10.5 Beams 717

9.10.6 Floors 718

9.10.7 Removing.Columns 719

9.10.8 Closing.Comments 720

9.10.9 Historical.Recap.of.Post-Tensioned.Concrete 722

9.10.10.Landmarks.in.Post-Tensioned.Buildings 724

9.10.11.Load.Balancing 724

9.10.12.Banded.Tendons 724

9.10.13.Irregular.Column.Layout 725

9.10.14.Cracking.in.Post-Tensioned.Slabs 725

9.11 Reinforced.Concrete.Special.Moment.Frames 726

9.11.1 Frame.Proportioning 727

9.11.2 Strength.and.Drift.Limits 727

9.11.3 Design.Principles 728

9.11.3.1 Strong-Column/Weak-Beam.Design 728

9.11.3.2 Avoid.Shear.Failure 728

9.11.3.3 Detail.for.Ductile.Behavior 728

9.11.4 Analysis 729

9.11.4.1 Stiffness.Recommendations 730

9.11.4.2 Foundation.Modeling 730

Chapter 10 Torsion 731

Preview 731

10.1 Concept.of.Warping.Behavior 742

10.2 Sectorial.Coordinate.ω′ 746

10.3 Shear.Center 748

10.4 Evaluation.of.Product.Integrals 749

10.5 Principal.Sectorial.Coordinate.ωs.Diagram 750

10.5.1 Sectorial.Moment.of.Inertia.Iω 750

10.5.2 Torsion.Constant.J 750

10.6 Calculation.of.Sectorial.Properties:.Worked.Example 750

10.7 General.Theory.of.Warping.Torsion 753

10.8 Torsion.Analysis.of.Shear.Wall.Building:.Worked.Example 755

10.9 Warping.Torsion.Constants.for.Open.Sections 763

10.10 Stiffness.Method.Using.Warping-Column.Model 766

Chapter 11 Seismic.Design:.A.Pictorial.Review 769

Preview 769

11.1 Figures.and.Tables.Explaining.the Fundamentals.of.Seismic.Design 770

Chapter 12 Steel.Buildings:.Bolted.and.Welded.Connections,.Gravity,.and.Lateral. Load-Resisting.Systems.and.Details 793

Preview 793

12.1 General.Considerations.for.Welds 793

12.2 Methods.of.Welding.Inspection 797

12.3 Field.Tolerances 798

12.4 Brittle.Fracture 799

12.4.1 Historical.Review 799

12.4.2 Brittle.Fracture.Characteristics 800

12.5 ASTM.Specifications.for.Structural.Shapes,.Plates.and.Bars, and Fasteners 801

12.6 Thermal.Effects.on.Structural.Steel 801

12.6.1 Effect.of.Heat.due.to.Welding 807

12.6.2 Use.of.Heat.to.Straighten,.Camber,.or.Curve.Members 807

12.6.3 Coefficient.of.Expansion 807

12.7 Bolted.Connections 810

12.7.1 Bolts.in.Tension 811

12.7.2 Bolts.in.Shear 811

12.7.3 Bolts.in.Bearing 812

12.7.4 Slip-Critical.Bolted.Connection 813

12.8 Bearing.versus.Slip-Critical.Connections 813

12.8.1 Bolt.Installation:.Snug-Tight.versus.Fully.Tensioned 814

12.9 Bolts.Subjected.to.Shear.and.Tension 815

Chapter 13 Composite.Buildings:.Structural.System.and.Details 817

Preview 817

13.1 Composite.Steel.Deck 818

13.1.1 Finishes 819

13.1.2 Venting 819

13.1.3 Wire.Mesh 819

13.1.4 Parking.Garages 820

13.1.5 Fork.Lifts 820

13.2 Specifications.for.Steel.Deck:.Overview 820

13.2.1 Material.and.Design 820

13.2.2 Finishes 821

13.2.3 Tolerances 821

13.2.4 Installation 821

13.2.5 Concrete 821

13.2.6 Site.Storage 822

13.3 .ANSI/SDI.(C1.0.Standard.for.Composite.Floor.Deck):.A.Brief.Review 822

13.4 Composite.Beams 826

13.4.1 AISC.Design.Criteria:.Composite.Beams.with Steel Deck and Concrete.Topping 828

13.4.2 AISC.Requirements:.General.Comments 830

13.4.3 Effective.Width 833

13.4.4 Positive.Flexural.Strength 834

13.4.5 Negative.Flexural.Strength 834

13.4.6 Shear.Connectors 834

13.4.7 Deflection.Considerations 836

13.4.8 Design.Outline.for.Composite.Beam 837

13.4.9 Composite-Beam.Design.Examples 839

13.5 Composite.Joists.and.Trusses 842

13.5.1 Composite.Joists 842

13.5.2 Composite.Trusses 842

13.6 Other.Types.of.Composite.Floor.Construction 845

13.7 Continuous.Composite.Beams 846

13.8 Nonprismatic.Composite.Beams.and.Girders 846

13.9 Moment-Connected.Composite.Haunch.Girders 848

13.10 Composite.Columns 849

13.10.1.Behavior 850

13.10.2.Encased.Composite.Columns:.Design.Overview 851

13.10.3.Filled.Composite.Columns:.Design.Overview 852

13.10.3.1 Encased.Composite.Columns:.AISC.Design.Criteria 852

13.10.3.2 Limitations 852

13.10.3.3 Compressive.Strength 853

13.10.3.4 Tensile.Strength 853

13.10.3.5 Shear.Strength 854

13.10.3.6 Load.Transfer 85413.10.3.7 Detailing.Requirements 85413.10.3.8 Strength.of.Stud.Shear.Connectors 85513.10.3.9 Filled.Composite.Columns:.AISC.Design.Criteria 85513.10.3.10 Limitations 85513.10.3.11 Compressive.Strength 85513.10.3.12 Tensile.Strength 85513.10.3.13 Shear.Strength 85513.10.3.14 Load.Transfer 85513.10.4.Summary.of.AISC.Design.Criteria.for.Composite.Columns 856

13.10.4.1 Nominal.Strength.of.Composite.Sections 85613.10.5.Encased.Composite.Column.Limitations 856

13.10.5.1 Compressive.Strength 85713.10.5.2 Shear.Strength 85713.10.5.3 Load.Transfer 85713.10.6.Filled.Composite.Column:.Limitations 858

13.10.6.1 Compressive.Strength 85813.10.6.2 Load.Transfer 85813.10.7.Combined.Axial.Force.and.Flexure 85813.11 Design.Tables.and.Details 858

Bibliography 879

Index 883

Preface

Tall buildings have a unique appeal, even an air of romance and mystery associated with their.design The.adoration.that.super-.and.ultratall.buildings.command.lies.in.their.apparent.freedom.from.gravity.loads—they.do.not.just.stand.tall,.they.seem.to.do.so.effortlessly.resisting.gravity.as.well.as.laterally.directed.force.generated.by.wind.gusts.and.seismic.ground.motions

tion.was.to.create.monuments.rather.than.human.habitats Today’s.structures,.on.the.other.hand,.are.human.habitats—not.allowed.by.economics.and.design.to.be.nearly.as.simple,.heavy,.stiff,.and.robust.as.their.relatively.recent.counterparts.such.as.the.Empire.State.Building.of.the.1930s.Although.tall.buildings.are.unique.from.certain.aspects.such.as.consideration.of.lateral.deflec-tion,.their.design,.in.a.manner.of.speaking,.is.similar.to.the.design.of.their.lower.brethren Thus.the.material.presented.in.this.book.applies.equally.to.not-so-tall.buildings.as.well

Tall.buildings.have.fascinated.humans.from.the.beginning.of.civilization—the.primary.motiva-This.book.is.an.outgrowth.of.my.previous.publications It.attempts.to.maintain.the.same.basic.approach:.first.to.establish.a.firm.understanding.of.the.behavior.of.structural.members.and.systems.and.then.to.develop.proficiency.in.the.methods.used.in.current.design.practice.with.particular.refer-ence.to.the.provisions.of.the.following.publications:

Much of the present-day design is carried out using commercially available computer software

or spreadsheets written by individuals for their particular needs It is generally recognized that.mere.proficiency.in.navigating.through.computer.software.is.inadequate,.and.often.dangerous,.for.successful.professional.practice Moreover,.code.provisions.and.procedures.are.subject.to.change.periodically,.oftentimes too.frequent.for.the.comfort.of.design.professionals To.understand.and.keep.abreast.of.these.rapid.developments.is.no.small.task To.do.so.successfully,.the.engineer.needs

a thorough grounding in the behavior of structural components and systems Familiarity in the.present-day.methodology.is.essential.to.design.structures.that.comply.with.legally.adapted.stan-dards.and.to.do.so.safely,.economically,.and.efficiently

The.fundamental.laws.governing.the.static.and.dynamic.analysis.of.structures.subjected.to.the.forces.of.nature.are.over.150.years.old Therefore,.anyone.who.claims.that.they.have.invented.a.new.fundamental.principle.is.a.victim.of.their.own.knowledge.gap The.real.challenge.in.writing.a.text.in.the.structural.engineering.field,.then,.is.to.describe.in.physical.and.practical.terms.the.underlying.theory.and.how.it.relates.to.the.modern.world,.where.structural.analysis.and.even.the.interpretation.of.analysis.results.are.typically.done.by.the.computer

Thus,.the.foremost.objectives.of.this.book.are.as.follows:

• posite.members.and.systems

To.promote.a.better.understanding.of.the.structural.behavior.of.steel,.concrete,.and.com-• To.develop.a.cohesive.wind-.and.earthquake-resistant.design.procedure.for.tall.building.structures.and.their.lower.brethren

• To.bridge.the.gap.between.two.design.approaches,.one.based.on.skill.and.experience.and.the.other.that.relies.upon.computer.skills,.to.imagine.the.design.possibilities.when.that.wonderful.ability—the.intuition.we.humans.have—marries.unfathomable.precision.and.numerical.accuracy.

• To.cultivate.imaginative.approaches.by.presenting.examples,.and.where.appropriate.relate.these.specific.examples.to.building.codes.and.standards.that.are.essential.and.mandatory.tools.of.the.trade

• To address the question frequently proposed to the designer by architects: “Can we do.this?”.In.tackling.this.seemingly.simple.question,.we.need.to.acknowledge.that.in.the.fast.paced.world.we.live.in,.the.time.frame.for.answering.such.questions.is.measured.in.days.and.even.in.hours What.is.needed.at.this.juncture.is.the.proverbial.back-of-the-envelope.analysis.that.confirms.the.applicability.and.efficiency.of.a.concept,.which.would.then.also.serve.as.a.check.of.computer.solutions

• To.promote.the.idea.that.design.is.a.creative.process.as.opposed.to.a.mere.execution.of.framing.proposals

• To.reiterate.the.adage.that.computers.assist.us.in.the.analysis.phase,.but.it.is.the.designer.who.harmonizes.system.components.so.as.to.optimize.both.cost.and.behavior

hensive.text.that.will.explore.the.world.of.steel,.concrete,.and.composite.materials.as.applied.to.the.construction.of.buildings,.particularly.those.that.are.super-.and.ultratall

Utilizing.the.aforementioned.goals.as.a.guide,.I.have.set.for.myself.a.challenge.to.prepare.a.compre-tured.to.show.how.to.use.imperfect.information.to.estimate.the.answer.to.much.larger.and.complex.design.problems To.do.so.requires.a.certain.intuitive.feel.for.numbers.as.well.as.an.appreciation.of.the.fact.that.the.“right.answer”.in.this.context.is.only.of.an.order.of.magnitude.of.a.more.precise.computer.solution,.but.good.enough.to.put.us.on.the.right.track The.whole.idea.is.to.break.seem-ingly intractable problems down to more manageable pieces that can be quickly approximated Thus,.I.attempt.to.base.the.entire.text.on.that.wonderful.ability.of.intuition.we.humans.have.devel-oped.in.visualizing.and.realizing.economical.structural.systems

Using.conceptual.thinking.and.basic.strength.of.material.concepts.as.foundations,.I.have.ven-Developments.in.the.last.decade.have.produced.many.slender.high-rise.buildings,.demanding.that.particular.attention.be.paid.to.their.complex.behavior.under.lateral.loads Economic.consid-erations.routinely.call.for.leaner.and.sparser.designs.that.increasingly.challenge.the.design.profes-sional.to.come.up.with.safe.and.economical.structural.solutions

In.today’s.engineering.practice,.it.is.obligatory.to.prepare.several.schematic.options.before.a.final.scheme.is.selected Even.experienced.engineers.find.it.difficult.to.readily.come.up.with.diversified.structural.schemes.because,.other.than.their.own.library.of.experience,.very.little.reference.material.is.available This.book.attempts.to.alleviate.this.problem.by.providing.a.systematic.basis.for.arriving.at.preliminary.structural.schemes

The.trend.in.building.design.today.is.for.the.architect.to.define.the.building.shape.while.the.structural.engineer,.as.a.facilitator,.comes.up.with.a.structural.system.that.fulfils.the.architect’s.dream.within.the.owner’s.budget.requirements This.trend.has.resulted.in.innovative.and.daring.structural.schemes Fortunately.for.the.layperson,.the.result.has.been.an.interesting,.varied,.and.flamboyant.architecture.that.adds.to.the.variety.and.interest.of.the.skyline.in.urban.cities

mill.design.as.well.as.with.the.less.usual.structural.solutions To.this.end,.emphasis.is.placed.in.this.book.on.the.state-of-the-art.solutions.that.have.evolved.as.a.natural.extension.of.the.proven.systems

Therefore,.there.is.a.need.today.for.the.structural.engineer.to.be.familiar.with.the.run-of-the-Structural.steel,.as.we.know.today,.has.been.with.us.for.well.over.a.hundred.years It.was.in.the.year.1894.that.the.first.specification.for.structural.steel.was.published,.and.an.examination.of.test.results.of.that.era.suggests.that.the.properties.of.this.early.steel.were.not.very.different.from.the A36.steel of the 1950s and 1960s The first design specifications for steel buildings published by the

American.Institute.of.Steel.Construction.(AISC).in.the.1920s.firmly.established.steel.as.a.building.material,.and.ever.since.its.growth.has.been.phenomenal.in.the.construction.of.buildings.and.bridges.Reinforced.concrete.has.been.known.to.humans.for.over.two.hundred.years However,.its.rec-ognition.as.a.viable.product.for.seismic.areas.and.loads.is.relatively.recent In.fact,.it.was.at.an.American.Concrete.Institute.(ACI).convention.held.in.San.Francisco.in.1980.that.reinforced.con-crete was presented as a modern, earthquake-resistant material capable of being at once strong.and.ductile Since.then,.we.have.witnessed.a.phenomenal.increase.in.its.load-resisting.and.ductile.properties.

At.first.glance,.composite.construction.may.appear.to.be.a.new,.emerging.technology,.but.in.reality.it.has.been.with.us.also.for.over.a.hundred.years However,.only.recently.has.its.use.been.officially.formalized.by.the.AISC We.can.now.design,.with.equal.assurance,.composite.buildings.in.areas.of.high.seismic.risk

tals.of.conceptual.thinking If.we.were.to.retain.these.skills.as.a.profession,.we.engineers.would.be.more.adept.at.identifying.what.is.critical.for.capturing.essential.behavior.of.the.structural.system.instead.of.addressing.every.component.of.design.independently Computer.analysis,.then,.works.to.solidify.and.extend.the.creative.idea.or.concept.that.might.have.started.out.as.a.sketch.on.the.proverbial.back.of.the.envelope Our.unique.gift.as.engineers.is.our.critical.thinking,.and.we.risk.shortchanging.ourselves.and.our.field,.in.general,.if.we.remain.convinced.that.the.output.of.volumi-nous.calculations.of.every.structural.member.is.proof.of.good.design

In.today’s.world.of.high.expectations,.we.seem.to.place.less.emphasis.on.learning.the.fundamen-siderations of wind- and seismic-resistant design is required for most building structures in the.United.States The.use.of.these.documents.can.be.daunting,.particularly.for.those.engineers.that.have.little.formal.training.in.seismology,.seismic.hazard.analysis,.structural.dynamics,.and.inelastic.behavior Given.this.perspective,.this.book.has.been.designed.to.provide.guidance.on.how.to.use.code-based.procedures.while.at.the.same.time.providing.sufficient.technical.background.to.explain.why.the.provisions.are.written.the.way.they.are Where.possible,.the.technical.background.is.pre-sented.simultaneously.with.the.explanation.of.the.building.code.provisions In.many.cases,.such.explanations.are.presented.as.part.of.a.series.of.detailed.numerical.examples.that.are.presented.throughout.the.book Information.is.provided.on.the.wind.and.seismic.detailing.requirements.of.structural steel, reinforced concrete, and composite structures in the context of building system.selection.and.behavior

When.designing.buildings.in.accordance.with.the.ASCE.7-10.Minimum.Loads.Standards,.con-The.first.three.introductory.chapters.present.a.discussion.of.various.loads.and.load.combinations.typically.used.in.building.design Tall.buildings,.like.their.lower.brethren,.are.utilitarian.creations Out.of.all.concerns.related.to.structural.design,.that.of.safety.is.paramount.as.it.is.directly.related.to.the.loads If.the.earth.did.not.pull,.the.wind.did.not.blow,.the.earth’s.surface.did.not.sink.or.shake,.and.the.air.temperature.and.humidity.did.not.change,.loads.would.not.exist,.and.a.formal.structural.design.would.be.unnecessary We.would.all.be.out.of.work This,.however,.is.not.the.case

In.Chapter.1,.we.discuss.basic.dead.and.live.loads,.the.two.types.of.loads.that.exert.gravitational.loads.on.buildings Dead.loads.are.the.self-weight.components.that.make.up.the.building,.while.live.loads.determined.on.the.basis.of.statistic.probabilities.include.all.the.loads.that.are.variable.within.the.operation.cycle.of.a.building

Chapter.2.discusses.the.wind.forces.that.must.be.accounted.for.in.a.properly.engineered.lateral.force.resisting.system,.regardless.of.building.size.or.magnitude.of.load Special.emphasis.is.on.the.technical.background.to.explain.why.the.code.provisions.are.written.the.way.they.are Methods.for.assessing.wind.loads.to.examine.building.performance.in.severe.windstorms.are.also.discussed

In.Chapter.3,.we.discuss.the.ground.and.building.characteristics.so.essential.to.give.designers.a

feel.for.how.their.building.will.react.to.ground.shaking The.chapter.emphasizes.the.fact.that.in.spite.of.the.complexity.of.the.interactions.between.the.building.and.the.ground.during.the.first.few.sec-onds.of.shaking,.there.is.ample.evidence.from.extensive.observations.of.buildings.in.earthquakes.worldwide.as.to.how.different.building.types.will.perform.under.different.shaking.conditions

Conceptual.seismic.design,.defined.here.as.the.avoidance.or.minimization.of.problems.created.by.the.effects.of.seismic.excitation,.is.discussed.in.Chapter.5 From.the.analysis.of.general.equations.for.predicting.earthquake.response,.it.becomes.clear.that.to.overcome.the.detrimental.effects.of.many.of.the.uncertainties.in.the.predictions,.one.needs.to.apply.a.two-pronged.approach:.(1).control.or.decrease.the.demand.as.much.as.possible.and.(2).be.generous.in.the.supply.of.capacity,.particu-larly.by.providing.large.ductility.with.stable.hysteretic.behavior,.also.called.toughness Using.this.philosophy.as.a.basis,.the.first.part.of.this.chapter.translates.the.complex.field.of.structural.dynamics.into.a.simplified.language.that.will.be.comprehensible.to.anyone.concerned.with.the.seismic.design.of.buildings The.primary.emphasis.is.on.visual.and.descriptive.analysis The.engineering.mechan-ics.is.kept.to.a.basic.level.and.the.mathematics.to.slide.rule.accuracy Design.requirements.of.ASCE.7-10.that.implicitly.provide.for.acceptable.performance.beyond.elastic.range.are.discussed.using.static,.dynamic,.and.time-history.procedures

In.Chapter.6lutionary,.it.represents.an.evolution.in.design.thinking.that.is.in.tune.with.the.increasing.complexity.of.today’s.buildings.and.also.takes.advantage.of.development.and.innovations.in.building.technol-ogy PBD.suggests.that.rather.than.relying.on.the.building.code.for.protection.against.seismic.haz-ards,.a.more.systematic.investigation.is.conducted.to.ensure.that.the.specific.concerns.of.building.owners.and.occupants.are.addressed Building.codes.focus.on.providing.life.safety,.and.property.protection.is.secondary;.PBD.provides.additional.levels.of.protection.that.cover.property.damage.and.avoidance.of.functional.interruption.within.a.financially.feasible.context

,.we.introduce.the.concept.of.performance-based.design.(PBD) Although.not.revo-tive.provisions.that.tend.to.discourage.innovation.required.of.ever.more.complex.buildings,.PBD.provides.analytical.tools.to.assist.in.the.earthquake.design.assurance.process It.is.expected.that.the.profession.will.be.able.to.avail.itself.of.PBD.techniques.within.this.decade This.is.so.because.owners.like.them.for.they.are.likely.to.cost.less.if.designed.only.for.traditional.code.compliance,.architects.love.them.because.it.offers.more.design.freedom,.and.engineers.being.thrifty.go.for.it.because.it.can.result.in.higher.quality.structures.with.the.least.amount.of.material

PBD.has.become.the.high-end,.cutting-edge.technology.in.building.design In.lieu.of.prescrip-Chapter.7oped.using.fundamental.principles.of.mechanics.because.it.is.only.through.sound.understanding.of.these.principles.that.engineers.can.successfully.perform.preliminary.designs.without.resorting.to.full-blown.computer.analysis The.chapter.concludes.with.a.discussion.of.preliminary.methods.for.determining.axial.shortening.of.tall.steel.building.columns,.and.graphical.aids.for.estimating.unit.quantity.of.structural.materials.for.the.purpose.of.conceptual.estimates

.presents.preliminary.analysis.and.design.techniques Approximate.methods.are.devel-Chapter.8.is.devoted.to.the.structural.rehabilitation.of.seismically.vulnerable.steel.and.concrete.buildings Design.differences.between.a.code-sponsored.approach.and.the.concept.of.ductility.trade-off for strength are discussed, including seismic deficiencies and common upgrade methods The.ASCE.standard,.Seismic.Rehabilitation.of.Buildings,.ASCE/SEI.41-06,.forms.the.basis.of.this.chapter

In.Chapter.9,.we.address.a.number.of.topics,.including.serviceability.considerations,.prediction.of.tall.building.motions,.damping.devices,.seismic.isolation,.blast-resistant.design,.and.progressive.collapse The.structural.systems.for.selected.tall.buildings.are.also.described

Chapter 10 covers warping torsion, as it applies to open-section shear walls and wide flange.sections It.includes.worked.examples.to.give.the.readers.a.feel.of.the.magnitude.of.axial.stresses.resulting.from.warping.torsion

Chapter.11.is.somewhat.unique.in.that.we.attempt.to.capture.the.essence.of.seismic.design.using.only.illustrations.with.elaborate.captions.where.necessary

Finally,.Chapters.12.and.13.are.dedicated.to.explaining.gravity.and.lateral.systems.for.steel,.and.composite.buildings,.respectively Also.discussed.in.these.chapters.is.the.nonquantifiable,.nonauto-matic.phase.of.design.that.engineers.call.their.art—the.art.of.connection.design

It.is.of.interest.to.recognize.that.the.debate.over.the.perceived.inadequacies.of.structural.engi-Additionally,.the.codified.laws.by.which.we.create.structures.have.also.expanded.and.sharpened The.bureaucratic,.legalistic,.rule-fixated.viewpoint.of.our.society.has.given.rise.to.building.codes.and.design.guidelines.that.are.voluminous.and.complex.without.precedent Gone.are.the.old.days.when.an.entire.code.book.was.no.more.than.an.inch.thick,.while.the.rest.of.the.design.process.was.left.to.the.engineer’s.specific.principles.and.experience

To be sure, today’s flamboyant architecture does not allow—by design and economics—structures.that.are.simple,.heavy,.stiff,.and.robust.as.were.the.buildings.of.the.1930s.and.1940s However,.even.in.today’s.computer.age,.the.same.timeless.principles.of.engineering.judgment.apply

as.much.now.as.ever.before,.demanding.that.we.perform.back-of-the-envelope.decision-making.

calculations.based.on.intuition.and.engineering.judgment

No.one.really.starts.with.intuition,.but.cultivates.it.slowly.over.time Computers.can.in.fact.help.the.engineer.develop.understanding.because.it.challenges.one’s.conventional.thinking The.trick.is

to.establish.a.link.between.those.who.have.knowledge.and.those.young.engineers.who.simply.run.

analytical.models Thus.a.business.office,.as.I.see,.also.becomes.a.place.of.continuing.education.between.masters.and.apprentices

What else can we do to prepare tomorrow’s engineers to design safe, cost-effective projects,.accounting.for.greater.complexity.and.uncertainty.with.less.formal.education?.The.answer.is.by.motivating.them.to.cultivate.engineering.judgment.and.intuition.with.a.constant.objective.of.educat-ing.oneself Every.moment.of.every.workday.can.be.a.learning.experience.practically.regardless.of.the.actual.task:.every.drawing.glanced.at,.or.an.engineering.conversation.overheard,.can.be.another.bit.of.experience.gained,.with.the.right.attitude

The.very.magnitude.of.efforts.required.to.achieve.the.said.goals.begs.for.a.communal.effort.on.a.national.scale The.work.presented.in.this.book.is.but.a.modest.attempt.by.a.single.author

plicated.with.each.edition,.and.there.seems.to.be.no.let.up.in.the.drive.of.code.writing.agen-cies.to.increase.the.complication Every.expert.in.the.field.wants.to.incorporate.what.he.or.she.considers.to.be.the.proper.structural.action,.typically.resulting.in.long.and.barely.understand-able.formulas It.has.gotten.so.that.in.many.cases.it.is.not.possible.to.understand.the.rationality.behind.these.equations

Design.specifications.for.steel,.concrete,.and.composite.construction.get.more.and.more.com-plished?.Do.we.have.better.structures?.Are.there.fewer.failures?.Have.we.balanced.the.complica-tions.against.the.need.to.maintain.simplicity.so.that.we.will.always.understand.the.structure?We.need.to.stop.and.take.a.hard.look.at.what.the.so-called.increased.precision.has.accomplished If.we.feel.that.the.specifications.are.not.accomplishing.their.purpose,.then.we.should.make.our.opinions.known It.seems.there.is.no.real.input.from.practicing.engineers.to.the.decision.of.code.writing.authorities

How.far.should.we.go.to.increase.the.complications?.What.have.the.super.specifications.accom-isfy.the.intent.of.the.code,.equations In.some.cases,.it.may.be.necessary.to.be.much.more.specific,.particularly.in.areas.that.are.fundamental.to.the.stability.of.structures Some.of.the.ideas.in.the.commentary.to.the.specifications.could.be.incorporated.with.much.more.discussion

One.answer.to.this.problem.is.perhaps.for.someone.to.write.a.simple.specification.that.will.sat-No.committee.could.do.this If.done.by.an.individual,.such.a.document.would.not.have.the.voice.of.authority,.but.if.it.was.well.done.it.would.be.used.with.confidence.by.practicing.engineers.The most important duty of engineers is to understand the structure they are designing If.this.is.not.accomplished,.then.there.is.a.risk.that.there.will.be.mistakes.that.will.cause.problems Specifications.ought.to.help.rather.than.hinder.this.process.

Tall Building Design: Steel, Concrete, and Composite Systems.addresses.the.foregoing.anxieties.while.integrating.the.design.aspects.of.building.structures.within.a.single.text It.is.my.hope.that.a.commonsense.approach.for.the.modern.world.presented.in.this.book.will.serve.as.a.comprehensive.design.guide.and.reference.for.practicing.engineers.and.educators,.and.more.importantly,.as.a.wel-come.mat.for.recent.graduates.entering.the.structural.engineering.profession.by.assuring.them.that.they.have.discovered.an.exciting.world.of.challenges.and.opportunity

Bungale S Taranath PhD, PE, SE

Structural Consultant Chino Hills, California

Acknowledgments

I.wish.to.express.my.sincere.gratitude.to.Samantha.Roy,.for.typing.the.manuscript.and.for.her.help.in.organizing.the.entire.manuscript.package

My.sincere.appreciation.and.thanks.to.Arun.Kumar.Aranganathan,.project.manager,.SPi.Global,.Pondicherry,.India,.for.the.elegant.layout.and.copyediting.of.this.book

sitions.editor,.CRC.Press,.Taylor.&.Francis.Group,.for.their.cooperation.in.the.production.of.this.book

Thanks.are.also.due.to.Jennifer.Ahringer,.production.coordinator,.and.Joseph.Clements,.acqui-Thanks in no small measure are due to my friend of many years, M.V Ravindra, CEO,.LeMessuirier.Consultants,.Boston,.Massachusetts,.for.his.valuable.advice.during.the.preparation.of.this.book

Everlasting thanks to my daughter, Dr Anupama Taranath; son, Abhi Taranath; son-in-law,

Dr. Rajesh.Rao;.daughter-in-law,.Kristin.Taranath;.grandsons,.Vijay.and.Kavi;.and.granddaughters,.Anika.and.Maya;.for.their.love.throughout.the.writing.of.this.book.that.stole.valuable.time.from.my.family.life

Special.thanks.to.my.daughter.Anu.for.taking.the.time.to.work.with.me.on.various.sections.of.this.manuscript My.sincere.thanks.to.my.son,.Abhiman.B Taranath,.for.typing.sections.of.the.manuscript

The.Publisher.wishes.to.thank.Syed.Mehdi.Ashraf,.Nate.Roy,.Mike.Mota,.and.Hans.William.Hagen.for.their.help.with.preparing.the.final.manuscript.for.publication

Special Acknowledgment

In.my.previous.five.books,.the.Acknowledgment.section.highlighted.the.extraordinary.support.my.wife.Saroja.has.offered.me.as.I.prepared.each.manuscript The.process.of.preparing.this.particular.manuscript,.however,.took.a.different.and.unexpected.turn.when.I.became.sick In.the.midst.of.all.the.health.challenges.we.faced,.the.camaraderie.and.good.humor.Saroja.showered.on.me.daily.liter-ally.helped.birth.this.sixth.book.into.being She.is.in.many.ways.my.coauthor.on.this.book.and,.in.life,.my.copilot For.her.incredible.care,.patience,.and.above.all.her.love,.I.thank.her.deeply Without.her,.my.humble.contributions.to.structural.engineering.would.not.have.been.possible

Bungale S Taranath

Chino Hills, California

Author

Dr Bungale S Taranath,.PhD,.PE,.SE,.was.a.structural.consultant.based.in.Chino.Hills,.California

He.had.extensive.experience.in.the.design.of.concrete,.steel,.and.composite.tall.buildings.and.served.as.principal-in-charge.for.many.notable.high-rise.buildings He.held.positions.as.a.senior.project.engineer in Chicago, Illinois, and as vice president and principal-in-charge with two consulting.firms.in.Houston,.Texas He.also.served.as.senior.project.manager.with.a.consulting.firm.in.Los.Angeles,.California Dr Taranath.was.a.member.of.the.American.Society.of.Civil.Engineers.and.the.Concrete.Institute.and.a.registered.structural.and.professional.engineer.in.several.states He.conducted.research.on.the.behavior.of.tall.buildings.and.shear.wall.structures.and.authored.a.num-ber.of.published.papers.on.torsion.analysis.and.multistory.construction.projects He.has.published

five.other.books: Structural Analysis and Design of Tall Buildings; Steel, Concrete, and Composite Design of Tall Buildings ; Wind and Earthquake Resistant Buildings: Structural Analysis and Design ; Reinforced Concrete Design of Tall Buildings; and Structural Analysis and Design of Tall Buildings: Steel and Composite Construction..Three.of.his.books.were.translated.into.Chinese.and.Korean.and.are.widely.referenced.throughout.Asia Dr Taranath.conducted.seminars.on.tall.build-ing.design.in.the.United.States,.China,.Hong.Kong,.Singapore,.Mexico,.India,.and.England He.was.awarded.a.bronze.medal.in.recognition.of.a.paper.presented.in.London,.when.he.was.a.fellow.of.the.Institution.of.Structural.Engineers,.London,.England Taranath’s.passion.for.tall.buildings.never.waned His.greatest.joy.was.sharing.that.enthusiasm.with.owners,.architects,.and.fellow.structural.engineers.to.develop.imaginative.solutions.for.seemingly.impossible.structures Dr Taranath.passed.away.as.this.book.was.being.produced

Preview

selves Thus,.there.are.two.basic.sources.of.building.loads:.geophysical.and.human.made

Loads.acting.on.a.structure.are.generated.either.directly.by.the.forces.of.nature.or.by.humans.them-vided.into.gravitational,.meteorological,.and.seismological.forces As.a.result.of.gravity,.the.weight.of.a.building.itself.produces.on.the.structures.forces.called.dead.load,.and.this.load.remains.constant.throughout.the.building’s.life.span The.ever-changing.occupancy.of.a.building.is.also.subject.to.gravitational.effects.producing.a.variation.of.loads.over.a.period.of.time Meteorological.loads.vary.with.time.and.location.and.appear.in.the.form.of.wind,.temperature,.humidity,.rain,.snow,.and.ice Seismological.forces.result.from.the.erratic.motion.of.the.ground

The.geophysical.forces,.being.the.result.of.continuous.changes.in.nature,.may.be.further.subdi-tors,.machines,.and.so.on,.or.they.may.be.the.movement.of.people.and.equipment.or.the.result.of.blast.and.impact Furthermore,.forces.may.be.locked.into.the.structures.during.the.manufac-turing.and.construction.processes The.stability.of.the.building.may.require.prestressing,.which.induces.forces

The.human-made.sources.of.loading.may.be.the.variations.of.shocks.generated.by.cars,.eleva-Geophysical and human-made sources for building loads are often mutually dependent The.mass,.size,.shape,.and.materials.of.a.building.influence.the.geophysical.force.action For.instance,.if.building.elements.are.restrained.from.responding.to.temperature.and.humidity.changes,.forces.are.induced.into.the.building

Relative.to.the.gravitational.forces.to.which.a.building.is.subjected,.loads.can.be.classified.into.two.distinct.categories:.static.and.dynamic Static.loads.are.always.a.permanent.part.of.the.struc-ture Dynamic loads are temporary: they change as time and season change or as a function of.spaces.within.or.on.a.structure

Dead.loads.may.be.defined.as.the.static.forces.caused.by.the.weight.of.every.element.within.the.structures The.forces.resulting.in.dead.load.consist.of.the.weights.of.the.load-bearing.elements.of.the.building,.floor,.and.ceiling.finishes,.permanent.partitioning.walls,.facade.cladding,.storage.tanks,.mechanical.distribution.systems,.and.so.on The.combination.weights.of.all.these.elements.make.up.the.dead.load.of.a.building

It.appears.to.be.a.simple.matter.to.determine.the.weights.of.materials,.thus.the.dead.load.of.a.structure However,.the.estimate.of.dead.loads.may.be.in.error.by.15%–20%.or.more.because.of.various.problems.in.making.an.accurate.analysis.of.the.loads At.an.early.design.stage,.it.is.impos-sible.for.the.analyst.to.predict.accurately.the.weight.of.building.materials.not.yet.selected Specific nonstructural.materials.to.be.chosen.include.facade.panels,.light.fixtures,.ceiling.systems,.pipes,.ducts,.electrical.lines,.and.components.of.special.interior.requirements The.weight.of.stiffening.elements.and.joinery.systems.for.steel.structures.is.estimated.only.on.a.percentage.basis The.unit.weights.of.materials.given.by.the.suppliers.are.not.always.consistent.with.those.of.the.final.manu-factured product The nominal sizes of building elements may differ from the actual sizes; the.formwork.for.cast-in-place.concrete.may.have.inaccuracies.of.½.in or.even.more

These.few.examples.indicate.that.in.the.absence.of.precise.information,.it.makes.sense.to.make.an.allowance.for.imprecision.in.calculating.dead.loads

DeaD LoaDs

Dead.loads.can.be.defined.as.vertical.loads.that.are.fixed.in.position.and.are.produced.by.the.weight.of.the.elements.of.the.structure.or.the.whole.structure.with.all.its.permanent.components Although.these.loads.are.known.quite.accurately.once.the.design.of.the.structure.is.completed,.at.the.begin-ning.of.an.analysis,.a.dead.load.has.to.be.assumed.as.close.as.possible Previous.design.experience,.available.data,.and.weight.tables,.as.well.as.some.empirical.formulas,.are.helpful.in.this.stage.of.the.design.process

Weights.of.building.materials.and.of.types.of.built-up.roofs.and.building.floors.can.be.found.in.handbooks.or.manuals

occupancy LoaDs on BuiLDings

All loads other than dead loads are live loads The live loading on buildings is highly variable,.depending.upon.the.use.of.the.building Minimum.values.are.usually.specified.by.local.or.national.building.codes Some.types.of.live.loads.may.be.practically.permanent.in.nature,.although.subject.to.removal.or.relocation Movable.partitions,.hung.ceilings,.and.building.equipment.fall.in.this.category.To.produce.a.safe.design,.occupancy.loads.are.taken.conservatively,.derived.more.from.experi-ence.and.current.practice.than.from.accurately.computed.values.from.statistical.data.based.on.the.probability.of.their.occurrence The.ASCE.7.gives.the.minimum.values.for.such.loads To.make.sure.these.loads.are.more.realistic,.allowance.is.made.for.some.percentage.reduction.from.the.full.loading

snow LoaDs on BuiLDings

During.the.winter.of.1979,.more.than.200.roofs.collapsed.in.the.northern.counties.of.Illinois.and.Wisconsin,.following.more.than.1300.collapses.in.the.northern.United.States.in.the.winter.of.1978 Subsequent.investigations.focused.on.two.problems.most.common.in.heavy.snow.areas:.unpredict-able.amounts.of.snow.and.the.nonuniform.distribution.of.it Roof.failure.caused.by.snow.usually.does.not.occur.as.a.result.of.a.uniform.load.but.from.a.localized.drift.or.ponding.load Wind.drifting.of.snow.has.been.the.root.cause.of.many.failures

The.current.ASCE.7.gives.a.basic.snow.load.P f

,.which.is.then.multiplied.by.the.appropriate.coeffi-cients.C e ,.C t

,.and.I The.basic.snow.load.corresponds.to.the.ground.load.in.psf.for.50.years.mean.recur-rence.interval.(MRI) These.loads.are.used.for.all.permanent.structures.except.those.that.are.judged.to.represent.an.unusually.high.degree.of.hazard.to.life.and.property.in.case.of.failure For.those,.a.100-year.MRI.must.be.used If.the.risk.to.human.life.is.negligible,.a.25-year.MRI.may.be.used ASCE.7-10.gives.a.map.of.the.United.States.showing.isolines.of.ground.snow See.ASCE.7-10,.Figure.7.1.The.snow-load.coefficient.depends.on.the.wind.speed.and.direction,.the.geometry.of.the.struc-ture,.and.the.temperature.gradient.between.the.inside.of.the.structure.and.the.outside The.basic

slope.factor.coefficient,.C s,.may.be.decreased.to.reflect.slide-off.of.snow.where.sloped.roofs.qualify,.based.on.their.roof.surface.roughness.and.whether.they.are.considered.to.be.warm.or.cold,.and.must.be.increased.to.reflect.nonuniform.accumulation.on.pitched.or.curved.roofs.as.well.as.in.valleys.formed.by.multiple.series.roofs

For.simplicity,.it.is.usually.assumed.that.forces.acting.on.building.structures.can.be.reduced.to.static.(unchanging).loads,.in.pounds.per.square.foot.(psf.or.kg/m2) In.fact,.these.loads.are.not.always.static Sometimes.they.are.dynamic,.changing.over.a.small.interval.of.time Live.loads,.seis-mic.disturbances,.gusting.of.wind,.movement.of.machinery,.or.any.other.source.of.fairly.rapid.load.variations.will.produce.dynamic.loads At.other.times,.they.are.produced.by.the.strain.and.move-ment.in.the.structure.caused.by.temperature.and.shrinkage Additional.strains,.and.thus.forces,.may.also.be.produced.by.the.uneven.settling.of.foundations,.even.though.dead-load.conditions.are.static.Nonetheless,.it.is.generally.possible.to.express.the.effects.of.these.more.or.less.changing.forces.in.terms.of.equivalent.static.load.in.psf

by.an.impact factor.that.yields.an.additional.statistical.load.as.a.percentage.of.the.basic.live.load.

Internal forces may also be produced in a building as a result of a temperature differential.between.various.parts.of.the.building In.this.situation,.one.part.of.a.structure.will.tend.to.resist.the.expansion.or.contraction.movement.of.another.part Relative.shrinkage.of.the.materials,.or.uneven.settling.of.foundations,.produces internal.forces.similar.to.those.of.self-stressing produced.by.a.temperature.gradient.within.the.structure.itself Each.condition.can.cause.unequal.movement.across.a.structure.that.can.produce.significant.forces.in.various.parts.of.a.building

In.this.opening.chapter,.we.study.the.effect.of.various.types.of.loads,.except.those.caused.by.wind.and.seismic Their.effects.are.considered.in.subsequent.chapters

1.1  DeaD LoaDs

The.engineer’s.first.job.is.to.determine.which.loads.will.act.on.a.structure.and.how.strong.they.might.be.in.extreme.cases Structural.engineering.would.be.unnecessary.and.we.would.all.be.out.of.work,.if.the.earth.did.not.pull,.the.wind.did.not.blow,.the.earth’s.surface.did.not.shake.or.sink,.and.the.air.temperature.and.humidity.did.not.change But.in.the.real.world,.we.must.concern.ourselves.with.all.the.loads.that.act.unavoidably.on.buildings

A.structure.consists.of.elements.like.columns,.beams,.floors,.arches,.or.domes.that.must,.first

of.all,.support.their.own.weight,.the.so-called dead.load And.here.lies.the.paradox.of.structural.

design To.determine.the.weight.of.a.structure,.once.the.dimensions.of.its.elements.are.established.and.the.material.chosen,.one.has.only.to.compute.the.volume.of.the.elements.and.multiply.it.by.the.weight.of.a.unit.volume.of.the.material The.trouble.is.that,.for.example,.in.order.to.make.sure.that.a.beam.will.carry.its.own.weight.and.other.loads.on.it,.we.must.first.know.its.dimensions,.but.these.in.turn.depend.on.the.beam’s.weight Thus,.structural.design,.the.determination.of.the.shape.and.dimensions.of.structural.elements,.can.only.be.learned.by.experience

The.dead.load.is.a.load.permanently there In.some.structures.built.of.masonry.or.concrete,.it.

is.often.the.heaviest.load.to.be.supported.by.the.structure By.the.way,.any.other.load.permanently.residing.on.the.structure.is.always.included.in.the.dead.load—the.weights.of.the.flooring,.ceiling,.and insulation materials, for example Similarly, the weight of permanent partitions—the walls.dividing.one.space.from.another.that.may.be.changed.or.shifted.in.rearranging.the.plan.of.a.build-ing.but.will.always.be.there—must.also.be.included.in.the.dead.load

ing including, but not limited to, walls, floors, roofs, ceiling, stairways, building partitions, fin-ishes,.cladding,.and.other.similarly.incorporated.architectural.and.structural.items.and.fixed.service.equipment.including.the.weight.of.cranes

Dead.loads.consist.of.the.weight.of.all.materials.of.construction.incorporated.into.the.build-To.establish.uniform.practice.among.designers,.the.ASCE.7.Standard,.Minimum.Design.Loads.for.Buildings.and.Other.Structures,.in.its.commentary,.Table.C3-1,.presents.a.list.of.materials.gener-ally.used.in.building.construction,.together.with.their.unit.weights A.condensed.version.of.the.table.is.given.here.in.Table.1.1

For.ease.of.computation,.most.values.are.given.in.terms.of.pounds.per.square.foot.(psf).(kN/m2) Pounds.per.cubic.foot.(lb/ft3).(kN/m3).values,.consistent.with.the.pounds.per.square.foot.(kilone-wtons.per.square.meter).values,.are.also.presented.in.some.cases Some.constructions.for.which.a.single.value.is.given.actually.have.a.considerable.range.in.weight The.average.value.given.is.suit-able.for.general.use,.but.when.there.is.reason.to.suspect.a.considerable.deviation.from.this,.the.actual.weight.should.be.determined

Although.engineers.cannot.be.responsible.for.circumstances.beyond.their.control,.experience.has.shown.that.conditions.are.encountered,.which,.if.not.considered.in.design,.may.reduce.the

TabLe 1.1 weights of building Materials

Ceilings

Channel.suspended.system 1 Lathing.and.plastering See.partitions Acoustical.fiber.tile 1

Corrugated.cement.asbestos.¼.in 3

Design.Loads.for.Buildings.and.Other.Structures,.2010.